A laundry treatment machine typically includes a cabinet wherein the processing chamber for housing the laundry to be treated is housed, and a door or porthole for providing access to and tightly closing the chamber. In the case of a washing machine or a washer/dryer, the chamber is usually a drum, rotatably mounted within a washing tub. In the case of a dryer, the chamber is usually a rotatable drum, there being air circulation ducts, a heater, and a blower for circulating heated air in the ducts and in the chamber.
A kind of porthole for laundry treatment machines which is of interest herein comprises an outer frame, an inner frame, and a glass sandwiched between the outer and inner frames. In the case of a circular porthole, the inner and outer frames are generally annular.
As used in the present description and in the attached claims, terms “outer” and “inner”, and “outwards” and “inwards” refer to the cabinet or the laundry treatment machine, and in the closed condition as far as the porthole is concerned.
Terms “radial”, “radially inner” and “radially outer” refer to the axis of rotation of the processing chamber, when the porthole is closed.
The glass is generally cup-shaped, having a flange retained between the frames, and protruding towards the inner of the laundry machine. An essentially disc shaped cap, e.g. made of transparent plastics, and/or a finishing rim may also be provided.
The porthole is typically hinged to the cabinet, so as to rotate (usually about a vertical axis), the hinge being usually arranged across a horizontal centerline or median plane of the porthole.
The porthole usually has a handle to be gripped by a user.
The porthole usually has an electromechanical lock. The electromechanical lock is usually configured to avoid opening of the porthole during operation of the machine; and to possibly avoid operation of the machine with the porthole open, by issuing a consent signal to an electronic control unit of the machine only when the porthole is closed and/or to delay opening of the porthole after the end of an operation cycle. The electromechanical lock is therefore also an interlock.
There are two major classes of door (or porthole) opening systems. In a first class, the porthole is provided with a hook that is moved by pivoting the handle with respect to the porthole, and the cabinet is provided with an opening that is engaged by the hook on the porthole in a closed condition, not engaged in an open or released condition. The portholes of this type suffer from the important drawback that they cannot be opened from inside the processing chamber (for example by a child who has entered the chamber and has closed the door), since their opening requires pivoting the handle (which can be clearly made only from outside the processing chamber).
In the second class of door opening systems, to which the invention is directed, and which may be named “pull-to-open type” door opening system, the porthole is provided with a latch, and the cabinet is provided with a latch retaining mechanism that includes a mobile part which is configured to be movable between a retaining position, in which it engages the latch so as to retain the porthole in a closed condition, and an opening position in which it releases the latch so as to allow the opening of the porthole. The mobile part of the latch retaining mechanism typically interacts with an elastic element, for example a spring, which allows the releasing of the latch when a releasing force is applied which is greater than a threshold force. The porthole is therefore opened by pulling it outwards with enough force, and can also be opened by pushing it from the inside of the drum, e.g. by a caught child.
Alternatively, the latch may be provided in the cabinet and the latch retaining mechanism may be provided in the porthole.
In the case of this second class, the handle of the porthole has only the function of providing a grip to the user, it is fixed to the outer frame of the porthole, and it is typically symmetrical with respect to the latch.